Federal kidnapping charges have been filed against a Denver woman in the case of a missing 6-day-old boy who disappeared in the middle of the night from his Wisconsin home.

The woman, Kristin Smith, could face life in prison if convicted of snatching her half-sister's newborn, Kayden Powell.

U.S. Attorney John Vaudreuil filed the charge against Smith on Friday afternoon, hours after the child was found alive near an Iowa gas station half a mile from where Smith was arrested.

Police recovered Kayden around 10:15 a.m. Friday, just a day after he disappeared from his home in Beloit, Wisc., while his parents and other family members were in the house.

"Despite frigid temperatures, Kayden was found alive and appears to be doing very well," Beloit Chief of Police Steve Kopp said in a statement. "In the words of the EMS officials, he is in 'excellent' health."

Police say Smith was at the house the night Kayden disappeared, but left the house around 1:30 a.m. without explanation to drive back to Colorado where she lives.

Kayden's mother, Brianna Marshall, 18, told authorities Thursday that she woke up around 4:30 a.m. to find her son gone, missing from his bassinet in the same room where she slept.

Investigators said there were no signs of a break-in at the home, and the parents were cooperative. The baby's father, Bruce Powell, 23, and two other people were also staying in the house, including Kristen Smith, police said.

Authorities were able to reach Smith on her cellphone, and she pulled off the highway in Iowa. Police arrested Smith at a convenience store along the highway on an outstanding fraud warrant from Texas. They found baby clothes, a fake pregnancy belly and a stroller in the woman's car, but not the baby. FBI agents then went to Iowa to question Smith.

The boy was found when the police chief of West Branch, Iowa, heard the baby crying, the Associated Press reported. The chief, who had been checking sites along Interstate 80 along with other officers, located the infant's cries and found the boy wrapped in blankets inside a bag.

Before Kayden was discovered, federal, state and local police combined forces to launch a massive search that included checking dumpsters, police said.

Kayden's maternal grandmother, Tracy Bennett, told ABC News affiliate WLS-TV on Thursday that Smith had spoken to her about moving the family to Colorado.